The first double execution in Oklahoma since 1937 was botched badly tonight when the cocktail of chemicals that was supposed to kill 38-year-old Clayton Lockett failed to actually kill him.

Various news reports and tweets from the McAlester prison where Lockett was held reported that the new cocktail included the sedative midazolam, which is normally used as a seizure medication. The drug has seen an increase of inclusion in the lethal injection process after the manufacturers of phenobarbital, the process’ previous sedative, forbade its use.

According to Bailey Elise McBride and Sean Murphy from the Associated Press:

The execution began at 6:23 p.m. when officials began administering the first drug, and a doctor declared Lockett to be unconscious at 6:33 p.m.

About three minutes later, though, Lockett began breathing heavily, writhing on the gurney, clenching his teeth and straining to lift his head off the pillow. After about three minutes, a doctor lifted the sheet that was covering Lockett to examine the injection site. After that, an official who was inside the death chamber lowered the blinds, preventing those in the viewing room from seeing what was happening.

Patton then made a series of phone calls before calling a halt to the execution. He also issued a 14-day postponement in the execution of inmate Charles Warner, who had been scheduled to die on Tuesday, two hours after Lockett was put to death.

Lockett allegedly died of a massive heart attack 20 minutes after the initial injection, though not much is known past that.

Oklahoma is one of 32 states that still carry the death penalty as punishment.